> I think the overhead for reading the aux.xml file is really minimal > and the min/max population of that if its not there is quite quick and > a once off event so I wouldnt think it is going to impact the server > much. I'd suggest I first run some benchmarks to see how much overhead > it adds.
But is there any downside from populating min/max on demand (e.g. like in QgsVectorDataProvider::minimumValue / maximum Value)? While it's nice to have a minimal overhead (probably buffered by the qgis server layer cache in many cases), it would be even better to have 0 overhead. Regards, Marco > Am Mittwoch, 10. August 2011, 11.50:16 schrieb Tim Sutton: > Hi > > On Wed, Aug 10, 2011 at 8:31 AM, Marco Hugentobler > > <marco.hugentob...@sourcepole.ch> wrote: > > Btw, is it possible to call computeMinMax() on demand, e.g. in > > QgsGDALProvider::minimumValue /maximumValue instead of the provider > > constructor? > > > > It probably does not matter much for the desktop experience. However, for > > server throughput, avoidance of opening and parsing the aux.xml file > > could make a difference. > > I think the overhead for reading the aux.xml file is really minimal > and the min/max population of that if its not there is quite quick and > a once off event so I wouldnt think it is going to impact the server > much. I'd suggest I first run some benchmarks to see how much overhead > it adds. > > Regards > > Tim > > > Regards, > > Marco > > > > Am Dienstag, 9. August 2011, 21.46:45 schrieb Tim Sutton: > >> Hi Paolo > >> > >> Does it do that every time you load that layer or only the first time? > >> Does the filesystem permissions allow writing of gdal .aux.xml files? > >> > >> My raster stats branch merge changed some behaviours and it is > >> probably a side effect of that. One of the changes is that gdal gets > >> full stats when trying to determine the min max of a band. It will > >> fetch those stats quickly from aux.xml if present of if not its going > >> to do a full stats gather just for the basic min max stats which is > >> where you probably experience the slowness. I will see if I can find a > >> better way to do the basic min/max stats gathering. > >> > >> Regards > >> > >> Tim > >> > >> On Tue, Aug 9, 2011 at 3:49 PM, Paolo Cavallini <cavall...@faunalia.it> > > > > wrote: > >> > Hi all. > >> > With current master, I get bad performances in loading rasters (a > >> > <12Mb takes >5 sec); when double-clicking it from the QGIS browser, > >> > it is far slower (>20 sec). From the console: > >> > Warning: Object::connect: No such signal > >> > QgsGdalProvider::statusChanged( QString ) in > >> > /storage/build/Quantum-GIS/src/core/raster/qgsrasterlayer.cpp:2446 Any > >> > hint? > >> > All the best. > >> > -- > >> > Paolo Cavallini: http://www.faunalia.it/pc > >> > _______________________________________________ > >> > Qgis-developer mailing list > >> > Qgis-developer@lists.osgeo.org > >> > http://lists.osgeo.org/mailman/listinfo/qgis-developer > > > > -- > > Dr. Marco Hugentobler > > Sourcepole - Linux & Open Source Solutions > > Churerstrasse 22, CH-8808 Pfäffikon SZ, Switzerland > > marco.hugentob...@sourcepole.ch http://www.sourcepole.ch > > Technical Advisor QGIS Project Steering Committee -- Dr. Marco Hugentobler Sourcepole - Linux & Open Source Solutions Churerstrasse 22, CH-8808 Pfäffikon SZ, Switzerland marco.hugentob...@sourcepole.ch http://www.sourcepole.ch Technical Advisor QGIS Project Steering Committee _______________________________________________ Qgis-developer mailing list Qgis-developer@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-developer